The Philippines and China has exchanged accusations of intentionally ramming coast guard vessels in disputed waters of the South China Sea on Saturday, the latest in an escalating series of clashes in the vital waterway.
The collision near the Sabina Shoal was their fifth maritime confrontation in a month, part of a longstanding rivalry.
Beijing claims almost the entire South China Sea, including parts claimed by the Philippines, Brunei, Malaysia, Taiwan and Vietnam.
Portions of the waterway, where $US3 trillion ($4.5 trillion) worth of trade passes annually, are believed to be rich in oil and natural gas deposits, as well as fish stocks.
The Permanent Court of Arbitration in 2016 found China's sweeping claims had no legal basis, a ruling Beijing rejects.
Philippine Coast Guard spokesperson Jay Tarriela showed videos of Saturday's confrontation at a press conference, saying China Coast Guard vessel 5205 "directly and intentionally rammed the Philippine vessel" without provocation.
The ramming damaged the Philippines' largest coast guard cutters, but no personnel were injured. (AFP: Philippines Coast Guard)
The ramming damaged the 97-metre Teresa Magbanua, one of the Philippines' largest coast guard cutters, but no personnel were injured, Mr Tarriela said.
Liu Dejun, a spokesperson for China's coast guard, said in a statement a Philippine ship, "illegally stranded" at the shoal, had lifted anchor and "deliberately rammed" a Chinese vessel.
He called on the Philippines to withdraw immediately or bear the consequences.
"The Chinese coast guard will take the measures required to resolutely thwart all acts of provocation, nuisance and infringement and resolutely safeguard the country's territorial sovereignty and maritime rights and interests," Mr Liu said.
Mr Tarriela said Manila would not withdraw its ship "despite the harassment, the bullying activities and escalatory action of the Chinese coast guard".
China's claims in the South China Sea cut through the majority of its neighbours' claims. (ABC News: Jarrod Fankhauser)
The US ambassador to the Philippines expressed Washington's support for the Philippines, a treaty ally.
"US condemns the multiple dangerous violations of international law by the PRC (People's Republic of China), including today's intentional ramming," Ambassador MaryKay Carlson said on social media platform X.
The Philippines deployed a ship in April to the Sabina Shoal, about 140 kilometres from the coast of the Philippine province of Palawan and 1,200 kilometres from China's Hainan island.
Manila accused Beijing of building an artificial island, saying it had documented piles of dead and crushed coral on the sandbars, which Beijing denies.
This week the Philippine maritime council said Chinese aircraft made unsafe manoeuvres against a civilian aircraft conducting patrols over two other disputed areas, the Scarborough Shoal and Subi reef.
The Philippines accused China of blocking a routine resupply mission on Sunday, saying Chinese vessels rammed and used water cannons on a fisheries bureau ship transporting food, fuel and medical supplies for Filipino fishermen.
Recent clashes between Philippine and Chinese vessels have also taken place around Second Thomas Shoal in the Spratly Islands.